In order to achieve better channel utilization and increase overall performance, multiple transmission and multiple reception antennas (also commonly referred to as multiple input, multiple output (MIMO)) at both evolved Node B (eNB) (or base station (BS), Node B (NB), communications controller, and the like) and User Equipment (UE) (or mobile station (MS), terminal, user, subscriber, subscriber equipment, and the like) are considered.
An extension to MIMO makes use of multiple communications points (each of which may be a set of geographically co-located transmit or receive antennas) to transmit or receive to or from a single UE or a group of UEs. As an example, the transmissions from the multiple transmission points may occur at the same time and/or the same frequency, or they may occur at different times and/or at different frequencies so that the UE (or the group of UEs) will receive transmissions from all of the multiple transmission points over a time window. This operating mode may often be referred to as multiple point transmission. As an example, at a first time, a first transmission point may transmit to a UE, at a second time, a second transmission point may transmit to the UE, and so on. Here the second time may or may not be the same as the first time.
Coordinated multiple point (CoMP) transmission is one form of multiple point transmission, wherein the transmissions made by the multiple transmission points are coordinated so that the UE or the group of UEs may be able to either combine the transmissions made by the multiple transmission points or avoid interference to improve overall performance. A transmission point may be an eNB, a part of an eNB (i.e., a cell), a remote radio head (RRH) connected to an eNB, or so on. It is noted that sectors of the same site, e.g., an eNB, correspond to different transmission points. Similarly, CoMP reception involves the reception of a transmitted signal(s) at multiple geographically separated reception points.
CoMP transmission and reception is being considered for inclusion in next generation wireless communications systems, such as in Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) Advanced standards compliant communications systems, as a tool to improve the coverage of high data rates, cell-edge throughput, and/or to increase overall communications system throughput in both high load and low load scenarios.
Generally, a handover (HO), which is also commonly referred to as a handoff, occurs when a user equipment changes from being served by a first communications point to being served by a second communications point.